NEUTRON-IRRADIATION EFFECTS ON CORRELATIONS BETWEEN MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF C C COMPOSITES/

Neutron irradiation effects on microstructure and mechanical propertie s of C/C composites were examined, and correlations between changes of mechanical properties and microstructure of composites were inspected . Materials used were one- and two-directionally reinforced composites with mesophase-pitch based carbon fibers as reinforcement and the mix ture of green coke and phenolic resin as matrix precursor. Neutron irr adiation was performed to 1.3 x 10(21) and 1.5 x 10(22) n/m(2) (E > 1 MeV) at about 350 K. Mechanical properties were measured by bend tests . Flexural and shear strength were increased with increasing neutron f luence. On the contrary, fracture strain showed quite a little depende nce on neutron fluence. Flexural modulus at near 0 strain was increase d with increasing fluence. Stress stiffening at near 0 strain was supp ressed with irradiation. While, modulus drop was observed at high stra in region and was decreased with increasing neutron fluence.